The processing of crude petroleum gives rise to various hydrocarbon fractions which may subsequently be "cracked" by heating, usually in the presence of steam, to produce a range of lower boiling products among which ethylene and propylene feature prominently. Naphtha (boiling range 32.degree. to 205.degree. C.) and gas oil (boiling range 205.degree. to 430.degree. C.) are suitable cracking feedstocks. As well as ethylene and propylene the cracked product also contains hydro-carbons of increasing molecular weight and boiling point from butenes through pentenes, hexanes, naphthenes, aromatics to cyclic and acyclic hydrocarbons of even higher carbon number. It is customary to fractionate these hydrocarbons by distillation into groups of compounds with similar boiling points. Thus, the C.sub.4 hydrocarbons removed as one fraction are followed by a range of compounds which may be designated for convenience as a C.sub.5 stream (although containing residual C.sub.4 hydrocarbon stream) predominating in C.sub.5 -C.sub.6 hydrocarbons containing 200 to 500 ppm H.sub.2 O, with or without further refining and with or without further additive reactants, which forms a suitable feedstock for the production of petroleum resins.
The resins, which vary in their properties as the hydrocarbon feedstock used in their preparation varies, are generally produced by treating the feedstock with a Friedel-Crafts polymerization catalyst, preferably a metallic halide, particularly aluminum chloride. The unsaturated hydrocarbons in the feedstock undergo homo- and co-polymerization reactions which give rise to a resinous product having softening points in the range of 85.degree. C. to 120.degree. C.
The Friedel-Crafts catalyst is generally taught to be used as a liquid ternary complex with a halogen hydroacid and: an aromatic compound (see U.S. Pat. No. 3,639,366 with equimolar amounts of aluminum chloride, hydrochloric acid and several alkylated benzenes); or a benzene which is liquid at the reaction temperature and which is substituted by at least one secondary or ternary alkyl or cycloalkyl group (see U.S. Pat. No. 3,763,125 where anhydrous AlCl.sub.3 and HCl are used to prepare the liquid ternary catalyst in cumene or p-cumene and see also U.S. Pat. No. 3,817,953, U.S. Pat. No. 3,865,797, and U.K. No. 1,408,870 which also teach complexing with toluene and xylene); or an alkylated benzene in combination with an alcohol or ether (see U.S. Pat. No. 4,076,926). In certain conditions when it is inappropriate to use the efficient ternary complex, much larger amounts of catalyst are required.
The polymerization reaction results in a polymerizate which is soluble in the hydrocarbon diluent present in the reactor and carried out from the reactor along with the catalyst which is subsequently water quenched and separated as an aluminous water waste product.
It is therefore highly desirable to increase the catalyst efficiency whereby greater resin yield is possible with less waste product which product is both an economic and environment debit.
It is an object of this invention to improve the catalytic efficiency of a Lewis acid, in particular AlCl.sub.3, catalyst in the production of petroleum resins.